1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to controlling transmission of content data, and more particularly, to controlling transmission of content data, in which a communication channel is initially established to transmit the content data, the content data is then transmitted through the established communication channel, verification is then performed a plurality of times to determine whether the content data is transmitted within an acceptable transmission range, and whether to continue the transmission of the content data is then determined according to the verification result.
2. Description of the Related Art
In a wired communication environment, data communication can be reliably achieved between devices since, once an initial session is established between a server and a client, the location of a receiving end and a data arrival time do not change while data is being transmitted. On the other hand, in a wireless communication environment, some problems may occur such as data transmission collision, data loss, etc. This is because several factors interrupt reliable communication in the wireless communication environment. Examples of such factors include use of a multi-path scheme, fading, interference, etc.
In the wireless communication environment, a server may determine an acceptable transmission range (or local range) in addition to an accessible range in which communication is available. Since a plurality of anonymous devices may receive radio waves in the accessible range in the wireless communication environment, the server must properly limit the acceptable transmission range.
In this case, a localization process is performed. The localization process is defined as a process of verifying whether a client is located within a limited acceptable transmission range. In general, the localization process is carried out by using a method of restricting a round trip time (RTT) of a packet transmitted between a server and a client so that the RTT is below a predetermined value.
FIG. 1 is a view for explaining a conventional method of transmitting content data between a server and a client.
Referring to FIG. 1, data has been conventionally transmitted between a server 110 and a client 120 in the following procedure. The client 120 requests the server 110 for content data (operation 130). In order to decide validity of the client 120, the server 110 performs an operation for mutual authentication and session key exchange (operation 140). For example, authentication and key exchange (AKE) is performed when using a digital transmission content protection over Internet protocol (DTCP/IP). The aforementioned localization operation is performed while exchanging a challenge key or an exchange key. When the AKE is successful, the server 110 transmits the content data requested by the client 120 (operations 150 to 170).
However, conventionally, the localization operation is performed only once when the AKE is carried out while an initial session is established, and thereafter the server 10 continuously transmits the content data to the client 120. Thus, the server 110 may continuously transmit the content data even when the client 120 is located at a later time in a position where a localization condition is not satisfied. In addition, localization may fail when interference temporarily occurs in the process of localization due to a certain obstacle, and thus the server 110 may stop the transmission of the content data.